1. Field of the Invention
This invention relates to a plug-type safety coupling for lines carrying high pressure media, said coupling having a coupling barrel with a locking element in its interior. The locking element is brought from a locking position to a working position or vice versa from a working position to a locking position by rotating it. The coupling may be used in lines handling compressible and non-compressible fluid media.
2. Description of the Prior Art
Plug-type security couplings are known in numerous variations and are commercially available, most such couplings having numerous individual components arranged axially, one behind the other, with respect to the line that is to be coupled and moveable in the direction of the axis. The operation of such plug-type couplings includes two elements that are functionally coupled: 1) the securing or blocking and un-blocking of the plug in the coupling barrel, and 2) the opening or closing of a valve that acts in an axially direction.
Despite costly solutions involving the most varied and complex components, known plug-type safety couplings still have dangerous aspects and are somewhat less than user-friendly. In many safety couplings, the plug is only locked in the coupling barrel once the blocking element has already opened, either partially or completely.
Thus, at that point the plug can be forcibly ejected from the coupling barrel.
In known safety couplings the operation of the plug-type coupling must be effected against the pressure exerted by the pressure media to be conveyed in order to move the blocking element in an axial direction and thus release or unblock the lines. Pressure lines having a large internal diameter can barely be coupled in this way at normal working pressures of 5 to 10 bar. The same is true for lines at corresponding negative pressures or vacuums. In these cases, one uses blocking valves which are disposed on both sides of the coupling and which remain independent of such coupling so that the coupling procedure its self is carried out when there is no pressure. In most cases, these blocking valves are automatic valves, mostly one-way valves. However, such valves limit the free flow of the medium to a considerable extent. For this reason, it is understandable that the pressure loss produced by such safety couplings can restrict the operation of the apparatuses and equipment which are to be operated and which are located at the end of the line.
In many compressed air couplings, a particularly dangerous situation occurs during the uncoupling procedure. In normal couplings, the line is blocked only shortly after the plug has been unlocked. If the line is not held with the plug securely in the hand, the plug can be forcibly ejected from the coupling by compressed air forces acting on it. Even in those cases in which, during the uncoupling procedure, the blocking element or the valve is closed and the unlocking is effected thereafter, the pressure of the compressed air which still remains in the uncoupled line cannot drop and the plug will be forcibly ejected from the coupling barrel.
Various proposals have been made in the past to solve these problems. The most elegant of these proposals incorporates a plug-type safety coupling that has, on one side, a plug which incorporates an enclosing, square cross-section bead, and, on the other side, a coupling barrel which is built up from a multi-part housing, in the interior of which is disposed a spherical blocking element to accommodate the plug. The blocking element is designed to be rotatable. The spherical blocking element has a continuous bore into which the plug can be inserted. The spherical blocking element can be pivoted into the operating position by a rotating movement of the plug which has been inserted. The plug is then secured in the housing in this working position by its bead and, thus, is secured against accidental withdrawal or against falling out. Rotation in the opposite direction moves the spherical blocking element into a locking position, the opening of the continuous bore passing over a release port through which any air which is still under pressure and remaining in the plug can escape, after which the plug can be withdrawn from the spherical blocking element in an unpressurized state. Because the blocking element in these couplings is a sphere or a ball, the housing of the coupling barrel must of necessity consist of a plurality of parts in order that the spherical blocking element can be sealed therein. In one embodiment, the housing consists of two halves having appropriately concave inner surfaces sealed together around the spherical blocking element. Connection of the two halves is effected by riveting.
In another embodiment, the housing consists of a shaped part in the interior of which the spherical blocking element is held by parts which are screwed into the shaped part. At one end, these parts are provided with a sealing element having a concave outer side which presses against the spherical blocking element. As previously discussed, the use of a sphere or a ball as a blocking element in these couplings requires that the housing of the coupling barrel be built from a plurality of parts. As a result, fabrication of this coupling involves a great deal of work and is correspondingly costly. The individual parts are relatively intricate and accordingly are costly to produce, and the assembly of the finished coupling involves a great deal of costly assembly labor due to the plurality of parts. In addition, from a technical point of view, supporting a sphere or ball against a seal is difficult. As a result, these known couplings have a tendency to leak under high pressures.